<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8"/>
        <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
        <meta http-equiv="X-UA-Compatible" content="ie=edge"/>
        <title>Document</title>
        <script>
            /* 
                url：统一资源定位符。

                协议://IP(域名)/:端口号/路径/?查询字符串#锚点
             */

            // alert(location.protocol);

            alert(location.hostname);
        </script>
    </head>
    <body>
        
    </body>
</html>